High precision independent positioning apparatus for reference station

ABSTRACT

An apparatus provides independent precise positioning for a reference station including a GNSS antenna and a GNSS receiver. The GNSS receiver generates GNSS data based on a plurality of GNSS signals received at the GNSS antenna, including GNSS signals having augmentation information. The apparatus includes a positioning processor, a signal processor, and a signal transmitter. The positioning processor calculates a current position of the reference station based on GNSS observation data and GNSS augmentation data obtained from the augmentation information included in the received GNSS signals, without using position information of another reference station, whereby the reference station is independently installed at a desirable location without surveying or measuring the desirable location. The signal processor generates error correction information including the current position of the reference station in a predetermined data format such as RTCM or CMR, based on the GNSS augmentation data.

CLAIM OF PRIORITY

This application is a Continuation of International Application No.PCT/IB2020/054235 which claims priority to U.S. Provisional PatentApplication No. 62/854,822, filed on May 30, 2019, each of which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a high precision positioning apparatusfor GNSS reference stations. More specifically, the present inventionrelates to an apparatus for providing high precision positioning for aGNSS reference station by implementing an independent positioningfunction such as Precise Point Positioning-Real Time Kinematic (PPP-RTK)or Precise Point Positioning (PPP) along with correction datageneration, such as RTCM, CMR, and the like.

Description of the Related Art

Global Navigation Satellite Systems (GNSS) available today includeUnited States Global Positioning System (GPS), Russian Global OrbitingNavigation Satellite System (GLONASS), European Union's Galileo, China'sBeiDou Satellite Navigation System (BDS, formerly known as Compass), andJapanese Quasi-Zenith Satellite System (QZSS).

In conventional relative positioning techniques such as Real TimeKinematic (RTK) positioning, Differential GNSS (DGNSS) technique, andthe like, it is necessary to have the precise position (coordinates) ofa reference station so as to generate error correction information suchas pseudo-range correction (PRC) information to improve positioningaccuracy. The PRC information created at the reference station isprovided via communication links, such as a radio beacon, NetworkedTransport of RTCM via Internet Protocol (NTRIP), Digital MultimediaBroadcasting (DMB), Radio Date System (RDS), FM data Radio Channel(DARC), etc. For example, Radio Technical Commission for MaritimeServices (RTCM) provides a transmission standard that defines the datastructure for differential correction information for a variety ofdifferential correction applications.

The more accurate the position of a reference station, the higher theaccuracy of positioning of a mobile station (rover receiver) using theerror correction information generated by the reference station, i.e.,the positioning solution becomes closer to the absolute position.Accordingly, it is necessary to conduct survey work with a high degreeof precision before installing a reference station with its preciseposition (initial-term coordinates). The tern “initial-term coordinates”may be used to indicate the coordinates at the time of installation ofthe reference station or that of a previous survey work performed in acertain year. In addition, since the position of the reference stationmay be changing due to diastrophism or crustal deformation, it is alsonecessary to continuously measure the installation position of thereference station in order to obtain its real-time position(current-term coordinates), since such a real-time position of thereference station is necessary for any mobile station or rover receiverto obtain its absolute position from its relative position with respectto the reference station.

The technique that continuously monitors and corrects the differencebetween the initial-term coordinates and the current-term coordinates iscalled dynamic correction. For example, GNSS Earth Observation networkSystem (GONET) in Japan includes a plurality (currently about 1,300) ofelectronic reference points (reference stations) and a single controlcenter. The signal from the GNSS satellite is continuously observed byeach of the reference stations for 24 hours, and the data acquired atthe reference stations is sent to Geodetic Observation Center of the GSI(Geographical Survey Institute, a.k.a. Geospatial Information Authorityof Japan) as raw observation data in a common format independent ofreceivers called RINEX (Receiver Independent Exchange Format). Theposition of each reference station is obtained only after theobservation data from the multiple reference stations is processed bythe server computers at the Center. Then, the Center publishes thereal-time position of the reference stations via the Internet, which isused by mobile stations or rovers (DGNSS users).

Conventionally, when a new reference station is installed, the location(precise position) of the new reference station is surveyed using DGNSSor RTK-GNSS, by concurrently conducting real-time GNSS observation atthe new reference station and another exiting reference station whichprecise location is known. Typically, the position is determined withthe accuracy of several meters using DGNSS, and that of sub centimetersusing RTK-GNSS. Due to a distance-dependent survey error, it isnecessary to have such an existing reference station near the locationat which the new reference station is to be installed.

It should be noted that Precise Point Positioning-Real Time Kinematic(PPP-RTK) is also referred to as Real Time Kinematic-Precise PointPositioning (RTK-PPP).

BRIEF DESCRIPTION OF THE INVENTION

An apparatus provides independent precise positioning for a GNSSreference station such that the reference station has a self-contained(i.e., independent) high-precision positioning function. Such areference station may generate error correction information. Inaddition, in accordance with one embodiment of the present invention,the reference station has the function of calculating and monitoring itsown position with high accuracy. Contrary to conventional referencestations, the reference station provided with the apparatus inaccordance with the present invention does not employ relativepositioning technology (such as RTK or DGNSS) using other referencestations. Instead, the reference station in accordance with the presentinvention uses satellite-based high-precision independent positioningtechnology in order to survey and determine the precise position of thereference station itself, for example, PPP using GNSS such as QZSS.

In other words, while a conventional reference station does not know itscurrent precise position since its initially-surveyed/measured positionwill change in time due to diastrophism or crustal deformation, asmentioned above, the reference station in accordance with the presentinvention independently obtains its current and updated precise positionbased on GNSS signals, thereby eliminating necessity of initial surveyand/or relative-positioning process for installation, and re-survey orre-measurement of the installation position for update thereof.

In accordance with one embodiment of the present invention, an apparatusprovides independent precise positioning for a reference station havinga GNSS antenna for receive a plurality of GNSS signals and a GNSSreceiver for generating GNSS data based on received GNSS signals. Theapparatus includes a positioning processor, a signal processor, and asignal transmitter. The positioning processor is capable of calculatinga current position of the reference station based on the GNSS datawithout using position information of another reference station. The asignal processor is configured to generate error correction informationin a predetermined data format based on the GNSS data, the errorcorrection information including the current position of the referencestation. The signal transmitter is configured to transmit the errorcorrection information via a communication link.

The plurality of GNSS signals may include GNSS signals havingcentimeter-level augmentation information. The GNSS data may includeGNSS observation data, and augmentation data obtained from theaugmentation information in the GNSS signals. The predetermined dataformat may be in accordance with standard correction data format of RTCMor CMR.

The positioning processor may repeatedly calculate and thereby monitorthe current position of the reference station.

The apparatus may further include a position memory that stores positioninformation of the reference station. The positioning processor mayrepeatedly calculates the current position of the reference station, andupdate with a certain time interval the position information in thememory with the current position. The signal processor may further beconfigured to generate the error correction information using theposition information stored in the position memory.

In accordance with one embodiment of the present invention, thepositioning processor may calculate a running average of the currentposition obtained during a predetermined time period, thereby obtainingan averaged position of the reference station, the averaged positionbeing stored in the memory as the position information.

The current position may be current coordinates of the referencestation, and the current coordinates may be geocentric coordinates. Thepositioning processor may be configured to perform Precise PointPositioning (PPP) or Precise Point Positioning-Real Time Kinetic(PPP-RTK).

In accordance with one embodiment of the present invention, theapparatus may be integrated in the GNSS receiver of the referencestation, or alternatively, the apparatus may be integrated within thereference station in communication with the GNSS receiver. In accordancewith one embodiment of the present invention, at least part of theapparatus may be external to the reference station and in communicationwith the GNSS receiver of the reference station.

In accordance with one embodiment of the present invention, a referencestation is equipped with a GNSS antenna configured to receive aplurality of GNSS signals and a GNSS receiver. The GNSS receiverincludes a positioning processor capable of calculating a currentposition of the reference station based on received GNSS signals withoutusing position information of another reference station, a signalprocessor configured to generate error correction information in apredetermined data format based on the received GNSS signals, where theerror correction information includes the current position of thereference station, and a signal transmitter configured to transmit theerror correction information via a communication link. The plurality ofGNSS signals may include GNSS signals having centimeter-levelaugmentation information. The predetermined data format may be inaccordance with RTCM standard, CMR standard, and the like.

The positioning processor may repeatedly or continuously calculate andthereby monitor the current position of the reference station.

In accordance with one embodiment of the present invention, the GNSSreceiver of the reference station may further include a position memorythat stores position information of the reference station. Thepositioning processor repeatedly or continuously calculates the currentposition of the reference station, and updates the position informationin the memory with the current position. The signal processor is furtherconfigured to generate the error correction information using theposition information stored in the position memory.

In accordance with one embodiment of the present invention, thepositioning processor may calculate a running average of the currentposition obtained during a predetermined time period, thereby obtainingan averaged position of the reference station. The averaged position isstored in the memory as the position information.

The current position may be current coordinates of the referencestation, and the current coordinates may be geocentric coordinates.

In accordance with one embodiment of the present invention, thepositioning processor performs Precise Point Positioning (PPP) orPrecise Point Positioning-Real Time Kinetic (PPP-RTK).

Another aspect of the present invention realizes a method for providingindependent precise positioning for a reference station having a GNSSantenna and a GNSS receiver. The method includes (a) receiving aplurality of GNSS signals from a plurality of GNSS satellites via theGNSS antenna, (b) obtaining GNSS data generated by the GNSS receiverfrom the plurality of GNSS signals, (c) performing positioning based onthe GNSS data to calculate a current position of the reference stationwithout using position information of another reference station, (d)generating error correction information in a predetermined data formatbased on results of the positioning, the error correction informationincluding the current position of the reference station, and (e)transmitting the error correction information via a communication link.

The plurality of GNSS signals may include GNSS signals havingcentimeter-level augmentation information. The GNSS data may includeGNSS observation data, and augmentation data obtained from theaugmentation information in the GNSS signals. The positioning may bePrecise Point Positioning (PPP) or Precise Point Positioning-Real TimeKinetic (PPP-RTK). The predetermined data format may be in accordancewith standard correction data format of RTCM or CMR.

In accordance with one embodiment of the present invention, the methodfurther includes installing, before the positioning, the referencestation at a desirable location without surveying or measuring thedesirable location, wherein the positioning is repeatedly orcontinuously performed after installation so as to monitor the currentposition of the reference station.

In accordance with one embodiment of the present invention, the methodfurther includes (c1) storing position information of the referencestation in a memory, (c2) repeatedly performing the positioning toobtain the current position of the reference station, and (c3) updatingthe position information in the memory with the current position. Theerror correction information may be generated using the positioninformation stored in the memory.

In accordance with one embodiment of the present invention, the methodfurther includes (c4) calculating a running average of the currentposition obtained during a predetermined time period, thereby obtainingan averaged position of the reference station, and (c5) storing theaveraged position in the memory as the position information.

The current position may be current coordinates of the referencestation, and the current coordinates may be geocentric coordinates.

In accordance with one embodiment of the present invention, theperforming positioning, the generating error correction information, andthe transmitting the error correction information may be performedwithin the reference station. Alternatively, at least one of thepositioning, the generation of error correction information, and thetransmission of the error correction information may be performedoutside the reference station in communication with the referencestation.

Another aspect of the present invention provides a method for installinga reference station at a precise location. According to this method, thereference station including a GNSS receiver having a positioningprocessor, an error correction signal processor, and a transmitter isprovided. The reference station is installed at a desirable locationwithout surveying or measuring the desirable location, and a pluralityof GNSS signals are received from a plurality of GNSS satellites via anantenna of the reference station. Positioning is performed using theGNSS receiver to calculate a current position of the reference stationbased on the received GNSS signals, without using position informationof another reference station or error information sent via anon-satellite communication link. Error correction information isgenerated in a predetermined data format based on the results of thepositioning, where the error correction information includes the currentposition of the reference station. Then, the error correctioninformation is transmitted via a communication link.

The plurality of GNSS signals may include GNSS signals havingcentimeter-level augmentation information. The predetermined data formatmay be in accordance with standard correction data format of RTCM orCMR.

In accordance with one embodiment of the present invention, thepositioning is continuously or repeatedly performed at a certain timeinterval so as to monitor the current position of the reference station.

In accordance with one embodiment of the present invention, a positionmemory that stores position information of the reference station may beprovided. The positioning is continuously or repeatedly performed toobtain the current position of the reference station, and the positioninformation in the memory is updated with the current position. Theerror correction information may be generated using the positioninformation stored in the position memory.

In accordance with one embodiment of the present invention, a runningaverage may be calculated for the current position obtained during apredetermined time period, so as to obtain an averaged position of thereference station. The averaged position is stored in the memory as theposition information.

The current position may be current coordinates of the referencestation, and the current coordinates may be geocentric coordinates. Thepositioning may be Precise Point Positioning (PPP) or Precise PointPositioning-Real Time Kinetic (PPP-RTK).

In accordance with the apparatus or the reference station according tothe present invention, it is always possible to obtain the currentcoordinates of the reference station, and thus it is unnecessary toperform semi-dynamic correction or dynamic correction.

Also, it is possible to install a new reference station in a short timewith high accuracy. Even if there are no other reference stations in thevicinity, the reference station according to the present invention canbe installed and its precise position is obtained. Once the referencestation is installed, maintenance such as re-surveying the position isunnecessary thereafter.

In particular, the reference station according to the present inventionor the reference station provided with the apparatus of the presentinvention may be employed as a portable base station used by severalworking sites. In such a case, it is not required to install thereference station at exactly the same position each time in each workingsite. It is possible to install the reference station at an arbitraryposition where the environment is more suitable for the satellitepositioning.

Since re-surveying for the installation of the reference station becomesunnecessary and thus the reference station can be installed at anysuitable position, it is possible to set up the reference station toprovide a shorter baseline for a rover which performs its own GNSSpositioning using the reference station, thereby improving thepositioning accuracy. For example, the reference station can beinstalled in any ideal place with the open sky and closer to the worksite.

Furthermore, since the reference station can be installed at any idealor suitable location, there is no need to use virtual reference station(VRS), and thus the operation cost can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the FIG.s of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 is a schematic diagram illustrating an implementation of areference station in accordance with one embodiment of the presentinvention.

FIG. 2A is a schematic diagram illustrating a conventional Precise PointPositioning by a rover in an environment with obstructing structures.

FIG. 2B is a schematic diagram illustrating an example in which a roverin an environment with obstructing structures is performing RTK usingerror correction information from the reference station in accordancewith one embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating an example in which aportable reference station in accordance with one embodiment is used fora plurality of work site.

FIG. 4 is a functional block diagram schematically illustrating thereference station in accordance with one embodiment of the presentinvention.

FIG. 5A is a functional block diagrams schematically illustrating anapparatus for providing independent precise positioning for a referencestation in accordance with embodiments of the present invention.

FIGS. 5B-5D are functional block diagrams schematically illustratingfurther examples of the apparatus for providing independent precisepositioning for a reference station in accordance with one embodiment ofthe present invention.

FIG. 6 is a block diagram illustrating a method for providingindependent precise positioning for a reference station in accordancewith one embodiment of the present invention.

FIG. 7 is a block diagram illustrating a method for installing areference station at a precise location without survey or measurement,in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention provides an apparatus for providing independentprecise positioning for a reference station, and such a referencestation with a self-contained high-precision positioning function suchthat the reference station continuously or repeatedly calculating andmonitoring its own position with high accuracy. “Self-containing” meansthat it does not employ relative positioning technology (such as RTK orDGNSS) which requires position information (known precise position) ofother reference station(s). That is, contrary to conventional referencestations, the reference station in accordance with the present inventionuses satellite-based high-precision positioning technology such as PPPor PPP-RTK using GNSS such as QZSS, without relying on other errorcorrection information or position information received vianon-satellite communication links such as the Internet. Such a referencestation may also generate and transmit error correction information.

FIG. 1 schematically illustrates an example in which the referencestation 10 in accordance with one embodiment of the present invention isimplemented. The reference station 10 may also be a reference stationprovided with the apparatus in accordance with the one embodiment of thepresent invention. The reference station 10 may be an electronicreference point installed at a fixed location. The fixed location may bea permanent location or a temporary location. The reference station 10may be a potable reference station used in different work sites asneeded.

As shown in FIG. 1, the reference station 10 receives a plurality ofGNSS signals from a plurality of GNSS satellites 20. The plurality ofGNSS satellites 20 are at least five GNSS satellites, and may includeGNSS satellites transmitting GNSS signals having centimeter-levelaugmentation (CLA) information therein. For example, QZSS satellitestransmit L6 signals having such centimeter-level augmentationinformation under the Centimeter Level Augmentation Information Service(CLAS) and Multi-GNSS Advanced Demonstration tool for Orbit and ClockAnalysis (MADOCA). The GNSS satellites which are capable of transmittingthe CLA information may be referred to as CLAS Satellites.

The reference station 10 performs positioning based on the received GNSSsignals and generates error correction information 30 including thecurrent position of the reference station 10, and transmits the errorcorrection information 30 via a communication link. For example, sucherror correction information 30 may use RTCM data format or CompactMeasurement Record (CMR) message format. The reference station 10 mayalso generate and transmit GNSS observation data.

As the error correction information 30 includes the precise position(current coordinates) of the reference station 10, as explained below,rovers (mobile stations) 40 such as vehicles, drones, or tractors, andother survey equipment (GNSS users) which also receive the GNSS signalsare able to calculate and determine their positions using the errorcorrection information 30 and the precise position of the referencestation 10 included therein. That is, such GNSS users (rovers 40)perform relative GNSS positioning so as to obtain their current positionbased on the current precise position of the reference station 10 bycalculating their relative position with respect to the current preciseposition of the reference station 10.

It should be noted that since a distance (baseline) between thereference station 10 and the rover(s) 40 is negligible compared with thedistance from the GNSS satellites 20, it is assumed that the rover(s) 40can use the same error correction information 30 as that for theposition of the reference station 10. Thus, the greater the distancebetween the reference station 10 and the rover(s) 40, the lesser theaccuracy of the relative GNSS positioning performed at the rover(s) 40.For example, the centimeter-level accuracy may be achieved up to thedistance of about 10 km. It may be desirable to perform such relativeGNSS positioning within 5 km range from the reference station 10 if therover receiver uses one signal frequency (for example, L1), or within 20km if the rover receiver uses two signal frequencies (for example, L1and L2).

Accordingly, since the reference station 10 can easily be installed at alocation close to the rover(s) 40, for example, several tens of meters,it is possible for the rover(s) 40 to use a simple radio or wirelessreceiver to receive the error correction information 30 from thereference station 10, without using the Internet, mobile phonecommunication system, or other public communication systems, which wouldrequire more complicated receivers. Thus, it is possible to reduce thecost of the receiver of the rovers 40, yet achieving the precisecentimeter-level positioning of the rover(s) 40.

Since the reference station 10 is able to obtain its own current preciseposition (installation location) solely based on the GNSS signalsreceived from the GNSS satellites 20, there is no need to perform surveywork for the installation location prior to the installation; conductinitial RTK positioning using an existing reference station within acertain distance, which also requires the Internet connection or thelike to receive error correction information for the exiting referencestation (to obtain the current position of the exiting referencestation); or re-survey the installation location to update the currentlocation after the installation. Accordingly, the reference station 10eliminates many procedural and locational requirements, limitations, andburdens.

It is also possible to select an ideal installation location for thereference station 10 to receive the GNSS signals, avoiding obstaclessuch as trees, tall buildings, and other structures blocking the signalpaths from the GNSS satellites. As the number of GNSS satellites thatuse the centimeter-level augmentation (CLA) information may be limited(for example, 11 satellites for CLAS), it is desirable and also possibleto set up the reference station 10 at such a location that the GNSSsignals including the CLA information are well received so as to performthe precise point positioning. That is, the reference station 10 can beinstalled at a position having a good view of the GNSS satellitesdesignated for CLAS among all visible GNSS satellites. The rovers 40 onthe other hand can use the error correction information 30 from thereference station 10 while performing multi-GNSS RTK positioning using alarger number of available GNSS satellites (including GPS, etc.) fromamong all visible GNSS satellites.

For example, conventionally, it may be possible for each rover (such astractor or construction machine such as a bulldozer) to perform precisepoint positioning to obtain its precise (centimeter-level) position inorder to perform automatic operation in an agriculture or constructionsite, and the like. However, surrounding structures such as tall treesor buildings may obstruct the view of the GNSS satellites using CLAinformation (for example, GNSS satellite 20 a), making it difficult forthe rover to fix the necessary GNSS signals, as shown in FIG. 2A. Byinstalling the reference station 10 in accordance with the presentinvention at an open area in the vicinity of the agriculture orconstruction site, as shown in FIG. 2B, the rover can switch itspositioning to RTK using the error correction information from thereference station 10 (including the current precise position of thereference station). In such a case, the rover can utilize a largernumber of GNSS signals available from visible GNSS satellites 20 toperform the relative-positioning, thereby achieving the centimeter-levelpositioning more stably.

As the reference station 10 is set up in a desirable location such as anopen area, it can receive GNSS signals from GNSS satellites 20 adesignated for CLA as well as other visible GNSS satellites 20. Thereference station 10 generates and transmits error correctioninformation for the visible GNSS satellites 20 (including theCLA-designated GNSS satellite 20 a) to the rover. Thus, although therover in a disadvantageous location may not be able to view all of theGNSS satellites which are visible from the reference station 10, therover still can perform RTK (relative positioning) satisfactoryutilizing available GNSS satellites with respect to the referencestation 10. Accordingly, the reference station 10 of the presentinvention makes the rover's centimeter-level positioning highlyadaptable to various environments and also to changes in theenvironment, by combining PPP (or PPP-RTK) at the reference station 10and RTK at the rovers utilizing the error correction information fromthe reference station 10.

In accordance with one embodiment of the present invention, thereference station 10 can be used as a temporary or potable referencestation. For example, as shown in FIG. 3, the reference station 10 isinstalled for Site A (for example, an agricultural field or constructionsite) at a suitable location such that a rover 40 a in Site A canperform the centimeter-level positioning (RTK) using the correctioninformation from the reference station 10 and its current preciseposition A. Then, when the work in Site A is completed or the referencestation 10 is not in use in Site A, the reference station 10 can bemoved to Position B for Site B in which a rover 40 b can utilize thereference station 10 and its error correction information to perform thecentimeter-level positioning, and so on.

FIG. 4 is a functional block diagram of the reference station 10 inaccordance with one embodiment of the present invention. As shown inFIG. 4, the reference station 10 includes a GNSS antenna 12 and a GNSSreceiver 14. In this example, the apparatus for providing theindependent precise positioning is implemented as the GNSS receiver 14in the reference station 10 so as to realize the reference station inaccordance with the present invention. The GNSS antenna 12 is configuredto receive a plurality of GNSS signals 22 from a plurality of GNSSsatellites 20, such as QZSS, GPS, and/or GLONASS. It is assumed that atleast five GNNS signals 22 are received by the GNSS antenna 12 andacquired and tracked by the GNSS receiver 14. The implementation of thepresent invention may be configured as a computer including a CPU, amemory (RAM, ROM), and the like therein so as to have the illustratedfunctional blocks. These functional blocks may be realized by means ofsoftware/computer programs realizing the respective functions, but apart or the whole of them may be realized by hardware.

As shown in FIG. 4, the GNSS receiver 14 includes a positioningprocessor 50 capable of calculating a current position of the referencestation 10 based on the received GNSS signals without using positioninformation of another reference station. For example, the positioningprocessor 50 performs Precise Point Positioning (PPP) or Precise PointPositioning-Real Time Kinetic(PPP-RTK). In accordance with oneembodiment of the present invention, the plurality of GNSS signals 22include GNSS signals having centimeter-level augmentation (CLA)information such that the positioning processor 50 obtains the currentposition of the reference station 10 with the centimeter-level accuracy.The positioning processor 50 may continuously or repeatedly calculateand monitor the current position of the reference station. It should benoted the positioning processor 50 includes a front end and othercomponents (not shown) to process the received GNSS signals as is wellunderstood by those of ordinary skill in the art.

As shown in FIG. 4, the GNSS receiver 14 further includes a signalprocessor 52 configured to generate error correction information in apredetermined data format based on the received GNSS signals processedby the positioning processor, where the error correction informationincludes the current position of the reference station. For example,such a predetermined format may be standard correction data format ofRTCM or CMR.

The positioning processor 50 and/or the signal processor 52 may alsogenerate conventional GNSS observation data. For example, thepositioning processor 50 may include GNSS data processor (not shown)which generates GNSS data from the received GNSS signals, where the GNSSdata includes GNSS observation data and the CLAS data. The GNSSobservation data may be generated from the GNSS signals in the frequencyrange L1 and/or L2 and/or L5, while the CLAS data may be generated fromthe GNSS signals in the frequency range L6. The positioning processor 50uses the GNSS data to obtain the current position, and the signalprocessor 52 generates the error correction information based on theGNSS data and the current position.

As shown in FIG. 4, the GNSS receiver 14 also includes a signaltransmitter 54 configured to transmit the error correction informationvia a communication link, such as a radio beacon, Networked Transport ofRTCM via Internet Protocol (NTRIP), Digital Multimedia Broadcasting(DMB), Radio Date System (RDS), FM data Radio Channel (DARC), etc. Thesignal transmitter 54 may be provided with two or more communicationlinks.

In accordance with one embodiment of the present invention, the GNSSreceiver 14 may further include a memory 56 that stores the positioninformation of the reference station 10. The memory 56 may be part ofthe positioning processor 50 or part of the signal processor 52, or maybe provided separately from the positioning processor 50 and the signalprocessor 52, so long as the memory 56 is accessible to both of thepositioning processor 50 and the signal processor 52. The positioningprocessor 50 continuously or repeatedly calculates the position of thereference station 10 so as to obtain current position of the referencestation 10, and updates the position information in the memory 42 withthe current position. The current position may be current coordinates ofthe reference station 10, and the current coordinates may be geocentriccoordinates of the reference station 10. The signal processor 52generates the error correction information using the positioninformation stored in the memory 56 such that the error correctioninformation always contains the updated current position of thereference station 10.

In accordance with one embodiment of the present invention, the memory56 may store the updated position of the reference station 10 for acertain period of time during which a plurality of updates areperformed. That is, the memory 56 holds a plurality of updates of thecurrent position, and the positioning processor 50 may calculate arunning average of the plurality of updates so as to obtain an averagedposition (averaged current coordinates). This averaged position isstored in the memory 56 as the position information of the referencestation 10 which is used by the signal processor 54 to generate theerror correction information. Since it is a running average, theaveraged position is also updated every time a new current position(coordinates) are obtained. The time period for the running average maybe 10 minutes, or more or less, for example.

FIG. 5A is a functional block diagram schematically illustrating anapparatus 200 a for providing independent precise positioning for areference station 210, in accordance with one embodiment of the presentinvention. Elements which may have the same or substantially the samefunction and/or structure are denoted with the same reference numeralsin the description. As shown in FIG. 5A, the reference station 210includes a GNSS antenna 12 and a GNSS receiver 214. The GNSS antenna 12is configured to receive a plurality of GNSS signals 22 from a pluralityof GNSS satellites 20, such as QZSS, GPS, and/or GLONASS. It is assumedthat at least five GNNS signals 22 are received by the GNSS antenna 12and acquired and tracked by the GNSS receiver 214. The implementation ofthe present invention may be configured as a computer including a CPU, amemory (RAM, ROM), and the like therein so as to have the illustratedfunctional blocks. These functional blocks may be realized by means ofsoftware/computer programs realizing the respective functions, but apart or the whole of them may be realized by hardware.

As shown in FIG. 5A, the GNSS receiver 214 includes a GNSS dataprocessor 60 for generating GNSS based on received GNSS signals. TheGNSS data is data generated from the GNSS signals and includes GNSSobservation data. It should be noted that the GNSS data processor 60includes a front end and other components (not shown) to process thereceived GNSS signals and produce the GNSS data, and the GNSS dataprocessor 60 may perform acquisition and tracking of the received GNSSsignals so as to produce the GNSS data, as is well understood by thoseof ordinary skill in the art. The GNSS observation data may include thetravelling time ΔT of the GNSS signal to propagate from the satelliteantenna (at the emission time) to the receiver (the receiver antenna12), for example. The plurality of GNSS signals 22 may include GNSSsignals having centimeter-level augmentation information (CLA), and thusthe GNSS data generated from the GNSS data processor 60 may furtherinclude augmentation data obtained from the augmentation information inthe GNSS signals.

For example, the GNSS observation data may be generated from the GNSSsignals in the frequency range L1 and/or L2 and/or L5, and thecentimeter-level augmentation data may be generated from the GNSSsignals in the frequency range L6. The GNSS data processor 60 mayprocess the received GNSS signals together to generate the GNSS dataincluding the GNSS observation data and the augmentation data.Alternatively, the GNSS receive 214 may be configured such that thereceived GNSS signals are divided according to the frequency range suchthat the GNSS data processor 60 processes the L1/L2/L5 signals and L6signals separately so as to generate the GNSS observation data and theaugmentation data through separate processing channels or usingdedicated data processors.

As shown in FIG. 5A, the apparatus 200 a is provided within thereference station 210 in this example. The apparatus 201 a includes apositioning processor 250 capable of calculating a current position ofthe reference station 210 based on the GNSS data obtained from the GNSSreceiver 214, without using position information of another referencestation. For example, the positioning processor 250 performs PrecisePoint Positioning (PPP) or Precise Point Positioning- Real TimeKinetic(PPP-RTK). As the plurality of GNSS signals 22 include GNSSsignals having centimeter-level augmentation information, as mentionedabove, the positioning processor 250 obtains the current position of thereference station 210 with the centimeter-level accuracy, using theaugmentation data as well the GNSS observation data in the GNSS data.The positioning processor 250 may continuously or repeatedly calculateand monitor the current position of the reference station. Suchcalculation may performed with a certain time interval, for example, inthe order of seconds, minutes, ten minutes, to a couple of hours.

As shown in FIG. 5A, the apparatus 200 a further includes a signalprocessor 52 configured to generate error correction information in apredetermined data format based on the GNSS data processed by thepositioning processor 250, where the error correction informationincludes the current position of the reference station 210. For example,such a predetermined format may be standard correction data format ofRTCM or CMR.

The apparatus 200 a also includes a signal transmitter 54 configured totransmit the error correction information via a communication link, suchas a radio beacon, Networked Transport of RTCM via Internet Protocol(NTRIP), Digital Multimedia Broadcasting (DMB), Radio Date System (RDS),FM data Radio Channel (DARC), etc. The signal transmitter 54 may beprovided with two or more communication links.

In accordance with one embodiment of the present invention, theapparatus 200 a may further include a memory 56 that stores the positioninformation of the reference station 210. The memory 56 may be part ofthe positioning processor 250 or part of the signal processor 52, or maybe provided separately from the positioning processor 250 and the signalprocessor 52, so long as the memory 56 is accessible to both of thepositioning processor 250 and the signal processor 52. The positioningprocessor 250 continuously or repeatedly calculates the position of thereference station 210 so as to obtain current position of the referencestation 210, and updates the position information in the memory 42 withthe current position. The current position may be current coordinates ofthe reference station 210, and the current coordinates may be geocentriccoordinates of the reference station 210. The signal processor 52generates the error correction information using the positioninformation stored in the memory 56 such that the error correctioninformation always contains the updated current position of thereference station 210.

In accordance with one embodiment of the present invention, the memory56 may store the updated position of the reference station 210 for acertain period of time during which a plurality of updates areperformed. That is, the memory 56 holds a plurality of updates of thecurrent position, and the positioning processor 250 may calculate arunning average of the plurality of updates so as to obtain an averagedposition (averaged current coordinates). This averaged position isstored in the memory 56 as the position information of the referencestation 210 which is used by the signal processor 54 to generate theerror correction information. Since it is a running average, theaveraged position is also updated every time a new current position(coordinates) are obtained. The time period for the running average maybe 10 minutes, or more or less, for example.

FIG. 5B is a functional block diagram schematically illustrating anapparatus 200 b for providing independent precise positioning for areference station 210, in accordance with one embodiment of the presentinvention. Elements which may have the same or substantially the samefunction and/or structure are denoted with the same reference numeralsin the description. As shown in FIG. 5B, the reference station 210includes a GNSS antenna 12 for receiving a plurality of GNSS signals,and a GNSS receiver 214 including a GNSS data processor 60 forgenerating GNSS data including GNSS observation data based on thereceived GNSS signals.

In this example, as shown in FIG. 5B, the apparatus 200 b is providedoutside of the reference station 210 in communication with the GNSSreceiver 214 such that the GNSS data from the GNSS data processor 60 isreceived by the positioning processor 250. The apparatus 200 b may bephysically attached to the reference station 210, or provided in theproximity of the reference station 210 via a short range communicationlink, or otherwise in communication with the reference station via anavailable communication link.

FIG. 5C is a functional block diagram schematically illustrating anapparatus 200 c for providing independent precise positioning for areference station 210, in accordance with one embodiment of the presentinvention. Elements which may have the same or substantially the samefunction and/or structure are denoted with the same reference numeralsin the description. As shown in FIG. 5C, the reference station 210includes a GNSS antenna 12 for receiving a plurality of GNSS signals,and a GNSS receiver 214 including a GNSS data processor 60 forgenerating GNSS data including GNSS observation data based on thereceived GNSS signals.

As shown in FIG. 5C, a part of the apparatus 200 c is external to thereference station 210 and in communication with the GNSS receiver 214.In this example, the positioning processor 250 is externally provided,while the signal processor 52 and the signal transmitter 54 are providedor installed in the reference station 210. The memory 56 may also beprovided in the reference station 210 separately from the signalprocessor 52 as shown in FIG. 5C, or integrated in the signal processor52. Alternatively, the memory 52 may be provided with or integratedwithin the positioning processor 250.

FIG. 5D is a functional block diagram schematically illustrating anapparatus 200 d for providing independent precise positioning for areference station 210, in accordance with one embodiment of the presentinvention. Elements which may have the same or substantially the samefunction and/or structure are denoted with the same reference numeralsin the description. As shown in FIG. 5D, the reference station 210includes a GNSS antenna 12 for receiving a plurality of GNSS signals,and a GNSS receiver 214 including a DNSS data processor 60 forgenerating GNSS data including GNSS observation data based on thereceived GNSS signals.

As shown in FIG. 5D, a part of the apparatus 200 d is external to thereference station 210 and in communication with the GNSS receiver 214.In this example, the positioning processor 250, the memory 56, and thesignal processor 52 are externally provided, while the signaltransmitter 54 is provided or installed in the reference station 210.Similarly to other examples, the memory 56 may be provided separatelyfrom the positioning processor 250 and the signal processor 52 as shownin FIG. 5D, or integrated in one of the positioning processor 250 andthe signal processor 52. Alternatively, the memory 52 may be providedwith or integrated within the positioning processor 250.

FIG. 6 shows a method 100 for providing independent precise positioningfor a reference station in accordance with one embodiment of the presentinvention. The reference station may be the reference station 210 in oneof the examples described above. By providing the independent precisepositioning, the reference station 210 may be easily installed at aprecise location without conducting a survey work. As shown in FIG. 6,the reference station including a GNSS antenna and a GNSS receiver maybe installed, before performing positioning, at a desirable locationwithout surveying or measuring the desirable location (102). A pluralityof GNSS signals are received from a plurality of GNSS satellites via theGNSS antenna of the reference station (104). The plurality of GNSSsignals may include GNSS signals having centimeter-level augmentationinformation. GNSS data including GNSS observation data is generated bythe GNSS receiver from the plurality of GNSS signals (106), andpositioning is performed based on the GNSS observation data to calculatea current position of the reference station (108). The positioning maybe Precise Point Positioning (PPP) or Precise Point Positioning-RealTime Kinetic (PPP-RTK). The positioning 108 is performed based on theobtained GNSS data without using position information of anotherreference station or error information.

Error correction information is generated (110) in a predetermined dataformat based on the results of the positioning. The error correctioninformation includes the current position of the reference station. Thepredetermined data format may be in accordance with standard correctiondata format of RTCM or CMR. Then, the error correction information istransmitted via a communication link (112). As the plurality of GNSSsignals 22 include GNSS signals having centimeter-level augmentationinformation, the GNSS data includes augmentation data obtained from theaugmentation information as well as the GNSS observation data. Thus, thepositioning process (108) obtains the current position of the referencestation 210 with the centimeter-level accuracy, using the augmentationdata. By receiving and using the error correction information having thecurrent position of the reference station, a rover or rovers are able toperform a centimeter-level positioning.

In accordance with one embodiment of the present invention, the positioninformation (calculated coordinates) of the reference station is storedin a position memory. The positioning may be repeatedly or continuouslyperformed to obtain the current position of the reference station with acertain time interval depending on the processing time and/or accordingto a specific implementation. Such a time interval may be the order ofsecond, or the order of minutes, ten minutes to fifteen minutes, or afew hours. The position information in the memory is updated with thecurrent position such that the error correction information is generatedusing the updated position information stored in the position memory.

FIG. 7 shows a method 120 for installing a reference station inaccordance with one embodiment of the present invention. The referencestation may be the reference station 10 described above. The referencestation is easily installed at a precise location without conducting asurvey work. As shown in FIG. 7, the reference station including a GNSSreceiver having a positioning processor, an error correction signalprocessor, and a transmitter is provided (122). The reference station isinstalled at a desirable location without surveying or measuring thedesirable location (124), and a plurality of GNSS signals are receivedfrom a plurality of GNSS satellites via an antenna of the referencestation (126). The plurality of GNSS signals may include GNSS signalshaving centimeter-level augmentation information. Positioning isperformed using the GNSS receiver to calculate a current position of thereference station (128). The positioning may be Precise PointPositioning (PPP) or Precise Point Positioning-Real Time Kinetic(PPP-RTK). The positioning 128 is performed based on the received GNSSsignals without using position information of another reference stationor error information sent via a non-satellite communication link.

Error correction information is generated (130) in a predetermined dataformat based on the results of the positioning. The error correctioninformation includes the current position of the reference station. Thepredetermined data format may be in accordance with standard correctiondata format of RTCM or CMR. Then, the error correction information istransmitted via a communication link (132), thereby enabling a rover orrovers to perform a centimeter-level positioning using the errorcorrection information with the current position of reference station.

In accordance with one embodiment of the present invention, the positioninformation (calculated coordinates) of the reference station is storedin a position memory. The positioning may be repeatedly or continuouslyperformed to obtain the current position of the reference station with acertain time interval depending on the processing time and/or accordingto a specific implementation. Such a time interval may be the order ofsecond, or the order of minutes, ten minutes to fifteen minutes, or afew hours. The position information in the memory is updated with thecurrent position such that the error correction information is generatedusing the updated position information stored in the position memory.

In accordance with one embodiment of the present invention, the positionmemory may be configured to hold a plurality of calculated coordinatesfor a predetermined time period. That is, a plurality of updates of thecurrent position obtained in the predetermined time period aremaintained in the position memory. In this embodiment, in thepositioning process 108, a running average may be calculated for thecurrent position obtained during the predetermined time period (therecent updates maintained in the position memory), so as to generate anaveraged position of the reference station. For example, the positionmemory may hold a predetermined number of updates corresponding to thepredetermined time period, in which the oldest update is discarded whena new update is added to the position memory. In this way, the averagedposition of the reference station is generated from the predeterminednumber of the most recent updates. The averaged position is also storedin the memory as the position information to be used in generating theerror correction information.

The current position may be current coordinates of the referencestation, and the current coordinates may be geocentric coordinates, asmentioned above.

In accordance with one embodiment of the present invention, thepositioning processor 50 and/or the signal processor 52 may furthergenerate GNSS observation data, including the current position of thereference station 10, and transmit the GNSS observation data to one ormore control center via the signal transmitter 54. For example, when thereference station 10 is implemented as an electronic reference point aspart of an observation/survey network, the positioning processor 50and/or the signal processor 52 may provide the GNSS observation data ina suitable data format for such network.

In accordance with the reference station according to the presentinvention, it is always possible to obtain the current coordinates ofthe reference station, and thus it is unnecessary to performsemi-dynamic correction or dynamic correction.

Also, it is possible to install a new reference station in a short timewith high accuracy. Even if there is no other reference station in thevicinity, the reference station according to the present invention canbe installed and its precise position is obtained. Once the referencestation has been installed, maintenance such as re-surveying theposition in the future is unnecessary, even if the installation positionchanged due to diastrophism or crustal deformation.

In particular, when the reference station according to the presentinvention is employed as a portable base station used by several workingsites, for example, it is not required to install the reference stationat exactly the same position each time in each working site. It ispossible to install the reference station at an arbitrary position wherethe environment is more suitable for the satellite positioning.

Since re-surveying for the installation of the reference station isunnecessary and thus the reference station can be installed at anysuitable position, it is possible to set up the reference station atsuch a position for a rover which performs its own GNSS positioningusing the reference station to obtain a shorter baseline, therebyimproving the positioning accuracy. For example, the reference stationcan be installed in any ideal place with the open sky and closer to thework site.

In addition, using the present invention, a base station (referencestation) can be quickly installed in an arbitrary location where thePPP/PPP-RTK service is available, and a plurality of inexpensive L1 RTKrovers can be used in a radius of ˜5 km around the base station.

Furthermore, since the reference station can be installed at any idealor suitable location, there is no need to use virtual reference station(VRS), and thus the operation cost can be reduced.

While this invention has been described in terms of several preferredembodiments, there are alterations, permutations, modifications, andvarious substitute equivalents, which fall within the scope of thisinvention. It should also be noted that there are many alternative waysof implementing the methods and apparatuses of the present invention. Itis therefore intended that the following appended claims be interpretedas including all such alterations, permutations, and various substituteequivalents as fall within the true spirit and scope of the presentinvention.

What is claimed is:
 1. An apparatus for providing independent precisepositioning for a reference station, the reference station including aGNSS antenna for receive a plurality of GNSS signals from a plurality ofGNSS satellites, and a GNSS receiver for generating GNSS data based onreceived GNSS signals, the plurality of GNSS signals including GNSSsignals having augmentation information, the apparatus comprising: apositioning processor capable of calculating a current position of thereference station based on GNSS observation data and GNSS augmentationdata obtained from the augmentation information included in the receivedGNSS signals, without using position information of another referencestation; a signal processor configured to generate error correctioninformation in a predetermined data format based on the GNSS data, theerror correction information including the current position of thereference station; and a signal transmitter configured to transmit theerror correction information via a communication link.
 2. The referencestation according to claim 1, wherein the augmentation information iscentimeter-level augmentation information.
 3. The apparatus according toclaim 1, wherein the predetermined data format is in accordance withstandard correction data format of RTCM or CMR.
 4. The apparatusaccording to claim 1, wherein the positioning processor repeatedlycalculates and thereby monitors the current position of the referencestation.
 5. The apparatus according to claim 1, further comprises: aposition memory that stores position information of the referencestation, wherein the positioning processor repeatedly calculates thecurrent position of the reference station, and updates with a certaintime interval the position information in the memory with the currentposition.
 6. The apparatus according to claim 5, wherein the signalprocessor is further configured to generate the error correctioninformation using the position information stored in the positionmemory.
 7. The apparatus according to claim 5, wherein the positioningprocessor calculates a running average of the current position obtainedduring a predetermined time period, thereby obtaining an averagedposition of the reference station, the averaged position being stored inthe memory as the position information.
 8. The apparatus according toclaim 5, wherein the current position is current coordinates of thereference station.
 9. The apparatus according to claim 8, wherein thecurrent coordinates are geocentric coordinates.
 10. The apparatusaccording to claim 1, wherein the apparatus is integrated within theGNSS receiver of the reference station.
 11. The apparatus according toclaim 1, wherein the apparatus is integrated within the referencestation.
 12. The apparatus according to claim 1, wherein at least partof the apparatus is external to the reference station and incommunication with the GNSS receiver.
 13. The apparatus according toclaim 1, wherein the positioning processor performs Precise PointPositioning (PPP) or Precise Point Positioning- Real Time Kinetic(PPP-RTK).
 14. A method for providing independent precise positioningfor a reference station having a GNSS antenna and a GNSS receiver, themethod comprising: receiving a plurality of GNSS signals from aplurality of GNSS satellites via the GNSS antenna, the plurality of GNSSsignals including GNSS signals having augmentation information;obtaining GNSS data generated by the GNSS receiver based on the receivedGNSS signals, the GNSS data including GNSS observation data and GNSSaugmentation data obtained from the augmentation information in thereceived GNSS signals; performing positioning based on the GNSS data tocalculate a current position of the reference station without usingposition information of another reference station; generating errorcorrection information in a predetermined data format based on resultsof the positioning, the error correction information including thecurrent position of the reference station; and transmitting the errorcorrection information via a communication link.
 15. The methodaccording to claim 14, wherein the augmentation information iscentimeter-level augmentation information.
 16. The method according toclaim 14, wherein the predetermined data format is in accordance withstandard correction data format of RTCM or CMR.
 17. The method accordingto claim 14, further comprising: installing, before the positioning, thereference station at a desirable location without surveying or measuringthe desirable location, wherein the positioning is repeatedly performedafter installation so as to monitor the current position of thereference station.
 18. The method according to claim 14, furthercomprising: storing position information of the reference station in amemory; repeatedly performing the positioning to obtain the currentposition of the reference station; and updating the position informationin the memory with the current position.
 19. The method according toclaim 18, wherein the error correction information is generated usingthe position information stored in the memory.
 20. The method accordingto claim 19, further comprising: calculating a running average of thecurrent position obtained during a predetermined time period, therebyobtaining an averaged position of the reference station; and storing theaveraged position in the memory as the position information.
 21. Themethod according to claim 14, wherein the current position is currentcoordinates of the reference station.
 22. The method according to claim21, wherein the current coordinates are geocentric coordinates.
 23. Themethod according to claim 14, wherein the performing positioning, thegenerating error correction information, and the transmitting the errorcorrection information are performed within the reference station. 24.The method according to claim 14, wherein at least one of the performingpositioning, the generating error correction information, and thetransmitting the error correction information is performed outside thereference station in communication with the reference station.
 25. Themethod according to claim 14, wherein the positioning is Precise PointPositioning (PPP) or Precise Point Positioning- Real Time Kinetic(PPP-RTK).